粘膜下腫瘍様の形態を呈し肛門周囲Paget病変を伴った肛門管の二重癌の1例

Double Cancer of the Anal Canal Associated with Perianal Paget's Disease, Report of a Case

要旨　患者は58歳，女性．1998年7月に下血を認め某病院を受診し，大腸内視鏡検査を受けるも異常なしと言われた．12月より再度下血を認め近医を受診し，直腸指診で肛門の硬結を触れるため当院へ紹介入院となった．注腸X線および内視鏡検査で直腸下端から肛門管にかけて複雑な形態を呈する粘膜下腫瘍様隆起を認め，腹会陰式直腸切断術を行った．腫瘍は直腸下端から肛門管にかけ左壁を中心に存在し，径7.5×4cmの1型の低分化型腺癌で，深達度はa₁，粘膜内に癌がみられたのは一部のみで，大部分が直腸・肛門管の粘膜下以下に浸潤していた．切除標本肉眼像では指摘できなかったが，病理組織学的検討の結果，肛門側に独立したもう1つの病変を認めた．肛門管の後壁を中心に存在し，径6×1.5cmの高分化型腺癌で，深達度はsm，扁平上皮内にPaget typeで浸潤していた．本例は特異な形態を呈し画像診断上示唆に富み，なおかつPaget病変を合併するまれな症例であるため，若干の考察を加え報告する．

　A 58-year-old woman visited a doctor complaining of anal bleeding and was referred to our hospital because of the anal tumor. Double contrast barium study and endoscopy revealed a submucosal tumor-like lesion from the lower portion of the rectum to the anal canal. Abdominoperineal excision of the rectum was performed. There was a protruded tumor, 7.5 × 4 cm in size. Histological examination revealed that the tumor was a poorly differentiated adenocarcinoma with subadventitial invasion. A large part of the tumor was covered with anorectal columnar epithelium. Another tumor was incidentally found in the anal canal at the anal side of the first tumor. The tumor was a superficial depressed type and was 6 × 1.5 cm in size. Histological diagnosis of the second tumor was made as a well differentiated adenocarcinoma with submucosal invasion invading the adjacent anal squamous epithelium with Paget type lesion.